Patent GB-535859-A (GB)
Title: Operating mechanism for electrical circuit breakers
IPC: H01H3/30
Filed: 1939-10-23
Abstract: 535,859. Automatic circuit-breakers. ALLMANNA SVENSKA ELEKTRISKA AKTIEBOLAGET. Oct. 23, 1939, No. 28469. Convention date, Oct. 24, 1938. [Class 38 (v)] A circuit-breaker is closed by energy stored in a helical spring which is arranged in a casing adapted to rotate freely during the closing operation, and acts during expansion on a screw moving in a nut which is stationary at the time, the screw being threaded out of the nut and acting on the breaker-shaft in the closing direction. One end of the spring 5 is fixed to the bottom of the casing 6 and the other to one part 4 of a coupling; the part 4 being slidable in slots in the casing. The co-operating coupling- part 16 is pinned to the screw which is in the form of a threaded rod 7, the upper part of which projects through the journal collar 1 of the casing 6 whereas the lower engages a nut 8 secured to a ratchet 9. A spring 11 urges a coupling part 19, feathered at 23 to a shaft 21, into engagement with the ratchet 9, and bears on a crown wheel 13, which is threaded on the lower end of the shaft 21 and carries a projection engageable with a coupling 25 pinned at 26 to the shaft. When the crown wheel is rotated by the motor-driven pinion 12 to stress the spring 5, the first movement lifts shaft 21 to raise the nut 8 clear of the bearing 2 and then the coupling 25 is engaged to rotate the shaft 21 and, through 9, 19, also the nut 8. As the casing 6 is held by the pawl 14, the screw 7 is drawn downwards into the nut and compresses the spring 5 through the coupling 4, 16. After a given travel, screw 7 engages a pin 20 in the bore of shaft 21, the pin carrying a cross-piece 22 working in a slot in an enlarged part of the shaft 21, the diameter of which enlarged part is equal to the length of 22. The latter thus depresses the coupling 19 clear of the ratchet 9, so disengaging the nut 8 from shaft 21. The pawl 14 is tripped by a member released by a coil, Fig. 4 (not shown), and is held in deflected position clear of the casing 6 by a further pawl which is only freed at the end of the closing movement. When the casing is freed by the pawl 14, the spring rotates it and raises the screw 7 through the coupling 4, 16. The screw 7 engages and lifts a roller 35 on the shaft 34, Fig. 3, which is mounted on the ends of a pair of levers 32, which are rotatable on the breakershaft 28 but normally coupled thereto by a toggle 38, 39 and lever 31 fast on the shaft. The common toggle-pivot is normally anchored by a further toggle comprising levers 40, 33 the latter being pivoted at 29 and retained by a latch 41 against the action of the breaker-opening springs (not shown). When 41 is tripped by coil 43 and shaft 28 rotates in the direction of the arrow and stretches the toggle 38, 39, the shaft 34 is retained by the projecting screw 7 until the spring-straining action of Fig. 1 takes place, whereupon the descent of 7 allows 34 to drop, so restoring the levers 33, 40 to the latched position. The upward movement of 7 closes the breaker, which is retained by engagement of pawl 37 with a projection on lever 39. If tripping occurs when 7 is already in its lowered position. the movement of 39 deflects the pawl 37 and allows 34 to drop at once on to the screw 7. When, during expansion of spring 5, the coupling part 4 reaches the top of casing 6, the screw 7 continues its movement until the coupling- parts disengage, the casing then continuing to rotate until the bearing-friction stops it.